Doing countless crunches and sit ups are by far the most common exercise mistake for anyone who wants to slim down their midsection. The thought is that doing hundreds of crunches and sit ups will work the abs so hard that the fat covering them will disappear. If this were true, you would see people walking around with toned and defined abs and a soft and flabby body everywhere else.
Here's something to think about: we're always focusing on the abs but you ever noticed that the people who have the best abs also have a great body everywhere else? This is by design - not by coincidence. The idea that doing lots of crunches is going to get you six pack abs is a myth that is known as "spot reduction". Fat burning is not a local phenomenon. When you do bicep curls your biceps do not pull fat from your arm for energy, so why would crunches reduce the fat around your waistline? More on that soon.
If you want to see your abs then know this:
It all comes down to the basics of losing body fat, which is calories in vs. calories out.
In order to lose body fat you need to create a caloric deficit, which means that your body is burning more calories than it is taking in. Your diet constitutes how many calories you are taking in and your level of physical activity is what constitutes how many calories you burn off (in addition to your resting metabolism).
The biggest problem with crunches and sit ups are that they do not give you a very big "bang for your buck" with regard to caloric expenditure. You can spend 15 minutes doing crunches and get your abs working very hard, but you will only burn a small number of calories. This is not enough to have a large impact on losing body fat.
A simple way to understand this is to think about the difference workload between total body exercise and crunches.
Here is an example to get you started.
If you do an intense total body circuit (ex. squats, pushups, mountain climbers) for 15 minutes and compare that to 15 minutes of crunches, which do you think will burn more overall calories?
The answer is the total body exercise because you are working more muscles which in turn makes you burn more calories. The more calories you burn the more fat you will lose on your entire body, thus exposing your abs to the world. This is why total body training is so effective for losing body fat. It gives you a big "bang for your buck" because you are able to get so much work done in a relatively short amount of time.
Doing hundreds of crunches and sit ups are simply not a very efficient way to spend your time exercising. Your goal with exercising to lose body fat is to burn a lot of calories and to boost your metabolism.
Despite this overwhelming evidence - the general consensus is that doing crunches and sit ups will help you lose belly fat. It is very common to hear questions such as "I am doing lots of crunches but my waistline is not getting any smaller, what am I doing wrong?"
It is not that crunches are absolutely "wrong"; it is just that they are one of the least efficient ways to burn calories. Trying to use only crunches as your primary means to burn significant calories is like trying to lower your body fat by doing bicep curls, calf raises, or tricep extensions. All of these exercises burn a small amount of calories, because they are working small muscle groups.
Getting six pack abs is simply a matter of having a low body fat percentage. Lowering your body fat comes from creating a caloric deficit that forces your body to use stored fat as energy.
Even though crunches are not the best way to lose belly fat, you will find in the next section that training your abdominals according to their true function can help you get tighter abs faster.
Once you have stripped off all the fat THEN crunches are the best way to sharpen, define, and create a head turning 6-Pack, right??
Keep reading and you'll see why.
Main Lesson: Getting six pack abs is largely a matter of losing body fat. Total body training burns more calories than crunches and sit ups, and it is a much more effective and efficient way of training to get the most benefit in the least amount of time.